1. Field of the Art This invention relates to a reinforcing three-dimensional woven fabric construction which is partially varied in thread orientation angle suitably for application to an unevenly functioning composite material, and a method for producing such woven fabrics.
2. Prior Art The present inventors proposed in their previous patent application, Japanese Laid-Open Patent Application H2-259148, a technology of weaving three-dimensional 4- or 5-axis woven fabrics with various fiber orientation angles in a facilitated manner by the use of a rotor-carrier type three-dimensional fabric weaving machine (hereinafter referred to simply as a "3D weaving machine" for brevity). According to the previously proposed method of weaving a three-dimensional fabric, as will be described hereinafter with reference to FIGS. 6 and 7, there are employed a large number of rotors which are arranged in a matrix of multiple rows and arrays alternately with thread carriers, which are gripped between rotors in adjacently confronting positions. The rotors are each provided with guide grooves on the four sides of its circumference in such a way as to grip the carriers between the guide grooves on the rotors in adjacently confronting cooperative positions and in a configuration corresponding to the sectional shape of the three-dimensional fabric to be produced. When one of adjacently confronting rotors is turned, the position of the associated thread carrier is shifted under guidance of the groove on the other one of the confronting rotors, and these actions of rotors and thread carriers are repeated to weave a three-dimensional fabric of a required shape. Besides, in such a weaving operation, the entire rotors are divided into two groups each consisting of rotors which are not located in adjacent positions in row and array. Rotors of one group are held stationary to serve as non-rotatable fixed guides while rotors of the other group are turned through 90.degree. or 180.degree. in one direction. In the next phase of operation, the rotors of the firstly turned group are held stationary to serve as non-rotatable fixed guides while the rotors of the other group are turned through 90.degree. or 180.degree. in the reverse direction. These weaving actions are repeated to weave a three-dimensional fabric.
According to the above-mentioned previously proposed technology, it is possible to obtain a three-dimensional woven fabric construction with an arbitrary fiber orientation angle, which can be used effectively for various purposes. However, the fabric as a whole has a uniform fiber orientation angle, so that, depending upon the use of the three-dimensional fabric, it fails to utilize the high-function fiber to a maximum degree.
Accordingly, it is desirable to make use of the high-function fiber more effectively by partially varying the fiber orientation angle in consideration of the stresses which would occur in various portions of the woven structure.